Effect of Combination between Phytase , Xylanase and Protease Enzymes in Different Growing Phases on Growth Performance and Carcass Characteristics of Broiler Chicks.

Four hundred and forty, one day old unsexed Arbor Acres broiler chicks were used to investigate the optimum impact of the combination between  phytase , xylanase and protease enzymes to low energy and protein broiler diets at different growing phases on growth performance, carcass characteristics and feeding cost. Chicks were randomly allocated into eleven treatments (5*2+1) included control group (C) and ten treatments divided into two groups without phytase (Ph) enzyme and with Ph (1000 FTU/kg during whole production period) every group had five nutritional plans (NP). The five NP based on using diet contained lower 150 kcal metabolizable energy (ME) and 10% of crude protein (CP) in each feeding phase (D diet). NP 1, chicks fed on D diet; NP2, chicks fed on D diet with supplemental protease enzyme (300000 units/kg diet) during starting phase only ( DP_s); 3, chicks fed on D diet with supplemental xylanase enzyme (16000 units/kg diet) during finishing phase only (DX_F); 4, chicks fed on D diet with supplemental protease enzyme during starting phase and supplemental xylanase enzyme during finishing phase at the same previous doses (DP_sX_F); 5, chicks fed on D diet with both supplemental protease enzyme and supplemental xylanase enzyme during all feeding phases at the same previous doses (DPX). Diets of C group was formulated to contain the nutritional requirements of Arbor Acers broiler chicks from all nutrients during the feeding phases. All diets were formulated to save the strain requirements from the rest of nutrients. All chicks were housed in open system broiler house and received the same managerial conditions and veterinary program during experimental phase (1-40 d of age). Parameters of growth performance, carcass characteristics and feeding cost were calculated. The recorded results showed that, Among NP chicks fed on D presented the worst growth performance during all feeding phases. During starting phase, FCR improved due to using DP_S, DP_S X_F  or DPX and the best value recorded by using DPX (1.56). While the recorded performance parameters during the finishing phase showed significant improvement of both BWG and FCR by applying DXP (1082) g and 1.78) or DP_S X_F (1055 g and 1.77). Also, phytase enzyme improved BWG and FCR significantly during all growing phases compared to performance of unsupplemented groups. The interactions between NP and phytase supplementation had significant effects on all growth performance parameters during all feeding phases. Both phytase supplementation and applying different NP caused significant effect on both cumulative FI and average daily gain (ADG) during the experimental phases. The overall results of carcass characteristics showed synergism effect of P, X and phytase (DPXPh) on dressing %, breast meat yield and thigh meat yield of broiler chicks beside the superior effect on growth performance parameters. The overall results confirmed the synergism effect between P, X and Phytase enzymes in broiler diets based on corn/soybean. The results recommended using combined supplementation of Phytase, P, and X to low 150 kcal of ME/kg and 10% of CP broiler diets during all growing phases to reach the same growth performance and better carcass, breast meat yield, thigh meat and economic benefits compared to control broiler chicks.